<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<div id="app">
  <!-- v-once固定显示第一次的值，不跟表达式 -->
  <h2 v-once>{{message}}</h2>
</div>

<script src="../js/vue.js"></script>
<script>
  const app = new Vue({
    el: '#app',
    data: {
      message: 'hi'
    }
  })

</script>
</body>
</html>